The Groupe Special Mobile (GSM) communication protocol includes two general classes of communications channels, dedicated channels and broadcast channels. The common channels are based on a 51 TDMA frame cycle including multiple Common Control Channel (CCCH) frames, Frequency Control Channel (FCCH) frames, and Synchronization Channel (SCH) frames. The CCCH may be an Access Grant Channel (AGCH) or a Paging Channel (PCH). Channel information is transmitted during multiple time-slots in consecutive frames. For example, every CCCH data block is transmitted in a series of four data bursts in corresponding time-slots of consecutive CCCH time frames.
It is known to conserve power in wireless communications devices operating in idle mode when not communicating by configuring radio circuits and a digital signal processor (DSP) in sleep mode. The microprocessor control unit (MCU) wakes-up the radio circuits and the DSP from sleep mode with a command when it is time to receive incoming data bursts, which are transferred to the DSP from the radio circuits. The radio circuits and DSP must remain awake to receive all data bursts in each data block, for example during the 1st, 2nd, 3rd and 4th time frames of a CCCH message. A command from the MCU on the final burst instructs the DSP to decode the PCH burst data. After the DSP decodes the burst data received, the DSP sends the decoded data to the MCU.
U.S. Pat. No. 5,570,369 entitled “Reduction of Power Consumption In A Mobile Station” discloses attempting to recover data bits of a four-burst message by de-interleaving data from at least 1st and 2nd bursts while assuming that data from the remaining bursts of the message are unreliable. The de-interleaved data bits are de-convoluted with a Modified Selective-Repeat Type-II Hybrid ARQ based de-convolution algorithm, and the result is FIRE decoded in an effort to reconstruct the original information. If reconstruction is unsuccessful, then a 3rd data burst is received and the de-interleaved data bits thereof are combined with the de-interleaved 1st and 2nd data bits, and the combined data bits are de-convoluted with a Viterbi algorithm before FIRE decoding. Power consumption of the device is reduced by operating radio circuits of the mobile station in sleep mode during the time frames when the 3rd and/or 4th bursts are transmitted if the original information may be reconstructed with only two or three data bursts. The methods of U.S. Pat. No. 5,570,369 require receiving at least the 1st and 2nd bursts of the four-burst PCH or BCCH message transmitted.
The various aspects, features and advantages of the present invention will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description with the accompanying drawings described below.